1. Field of the Invention
The embodiments discussed herein are related to a semiconductor device and a method of outputting a temperature alarm.
2. Background of the Related Art
Semiconductor devices called intelligent power modules (IPMs) that incorporate insulated gate semiconductor elements (insulated gate bipolar transistors or “IGBTs”) and drive circuits for driving the IGBT have been increasingly developed in recent years.
IPMs are power converting modules and are widely used in applications such as AC (Alternating Current) servos, air conditioners, and elevators.
IPMs also have a protector function capable of protecting abnormal circuits and elements when an abnormal state has been detected. As one example, when overheating has been detected, an IPM protects elements by avoiding the overheated area and outputs an alarm to the periphery.
As one example of existing technology, a configuration where the temperature of a semiconductor switch is constantly monitored by inputting the forward voltage drop of a temperature-detecting diode into a regulator and outputting the regulator output to an external terminal has been proposed (see Japanese Laid-open Patent Publication No. 2013-183595).
Another proposed technology determines that there is an abnormality when the chip temperature of a semiconductor switching element exceeds a first predetermined value that is above normal temperature and outputs an advance warning when the chip temperature exceeds a second predetermined value that is above the normal temperature but lower than the first predetermined value (see Japanese Laid-open Patent Publication No. 2000-341960).
A protector function incorporated in an IPM protects the semiconductor elements provided in the IPM during an abnormal state to avoid breakage, so that when an abnormality is detected, the IPM stops driving the IGBT.
This means that it is possible to avoid breakage of internal elements when the IPM has detected an abnormality, but since the driving of the IGBT is stopped by this protector function, an apparatus that is supplied with power from the IGBT may suddenly stop.
According to Japanese Laid-open Patent Publication No. 2000-341960, since an advance warning is outputted before the IPM detects an abnormality and the driving of the IGBT is stopped, a situation where the apparatus that is supplied with power suddenly stops is avoided.
However, with this technology, although it is possible to use a configuration where the advance warning signal is outputted from the same terminal as the alarm signal and use different signal widths for the respective signals, it is not possible to distinguish between the signals until an amount of time corresponding to the signal widths has passed.
Even when a warning signal is outputted when there are signs of an abnormality, control to output an advance warning quickly or slowly in keeping with the operational state of the IPM is not performed.
When an abnormal state of an IPM is very urgent, it is desirable to output an advance warning quickly. Conventionally however, advance warnings have been outputted without regard for the degree of urgency, so that there is the risk of delays in the IPM control system taking suitable measures for the IPM.